In order to explore the effect of mechanical weeding under straw mulching condition, the research was conducted in field experimental condition and two different treatments were set, mechanical weed control and chemical weed control. The species and number of weeds, soil temperature, yield and economic benefits were investigated and analyzed in maize and soybean production process. The results showed that although the number of weeds decreased with mechanical weed control for maize and soybean, the weed density was still 36.50 plants/m² and 28.25 plants/m²,which was 8.1 and 4.5 times higher than that of chemical weed control, respectively. Under the mechanical weed control, the 5 cm soil temperature of maize was improved 0.75℃, but 10 cm and 15 cm soil temperature of maize and soybean were reduced 0.57℃, 0.69℃ and 1.03℃, 1.27℃ respectively in high temperature period（from June 26 to July 19）. Compared with chemical weed control, the yield of mechanical weed control was reduced by 29.0% and 38.0% for maize and soybean, and the net profit decreased by 4 372.5 yuan/ha and 4 317.6 yuan/ha, respectively. Therefore, mechanical weed control reduces the yield and economic benefits and chemical weed control is more effective under the current experimental conditions.